Combustors used in gas turbine engines, for example those engines used for powering aircraft, typically include sheet metal combustion liners and sheet metal combustion dome assemblies. The combustor is provided with pressurized, compressed airflow from the gas turbine engine compressor and is, therefore, subject to pressure loading from the compressed airflow which will deform and buckle the combustor unless suitable stiffening structural support is provided to the combustor.
Furthermore, the compressor includes circumferentially spaced rotor blades which provide the compressed airflow with pressure pulses. Accordingly, the combustor must also be configured for accommodating these pressure pulses for providing acceptable vibratory life.
A typical gas turbine engine combustor includes a single annular dome having a plurality of circumferentially spaced carburetors which provide a fuel/air mixture into the combustor. Each of the carburetors includes a conventional fuel injector for providing fuel, and a conventional typically counterrotational swirler which provides swirled air for mixing with the fuel. Such single dome combustors have a relatively high length-to-height ratio for obtaining, for example, acceptable mixing of the combustor gases for generally uniform combustor exit temperatures. In order to reduce the length-to-height ratio for reducing weight and exhaust emissions, including for example NO.sub.x emissions, double dome annular combustors are being considered.
A double dome annular combustor includes radially outer and inner domes each including a respective plurality of circumferentially spaced carburetors. Each of the domes has a respective combustion zone extending downstream therefrom, each having a respective length-to-height ratio which is generally equal to length-to-height ratios of conventional single dome combustors. However, the overall length of the double dome combustor may be made substantially smaller than the length of a single dome combustor since the two combustion zones operate in parallel.
Since a double dome combustor has two radially extending domes which typically have an increased surface area the domes are subject to relatively high pressure loading from the pressurized compressed airflow provided from the compressor. For example, in one design application, the resultant axial pressure loading acting upon the double domes of an exemplary combustor is on the order of 15,000 pounds (about 6,800 kilograms) which is a substantial amount of loading which must be accommodated by the combustor without unacceptable distortion, buckling, or high cycle fatigue (HCF) life.
In one exemplary double dome combustor, an annular centerbody is bolted to the dome between the outer and inner rows of carburetors for providing additional structural stiffness for the double dome. Futhermore, for providing yet additional structural stiffness for accommodating the high pressure loading on the double dome, it is known to provide a plurality of circumferentially spaced, radially extending stiffening struts between the outer and inner domes which support the dome end of the combustor to liner supports. However, the centerbody and struts add complexity, weight, and cost to the combustor design.